So, I have a Cory Cat in an 150G tank, he is by far the cutest! But he acts strange most off the time, whenever we look for him we immediately look in a corner of the tank because he's usually "sleeping" is it possible for a Cory cat to have a sleeping disorder? He'll swim around for a bit and then sleep, swim a bit then sleep? And it goes on and on almost like he just passes out? What is going on with him? Is this normal? Is he dying?